1. Field of the Invention
This invention relates to a piston for an internal combustion engine, the piston having a pre-formed liner. The invention also relates to a method for manufacturing a piston assembly including a piston body and the liner.
2. Related Art Statement
The quest for favorable fuel consumption and power output has led to various designs for improving pistons and the materials from which they are made. Additionally, manufacturing techniques have been refined in pursuit of these goals.
U.S. Pat. No. 4,667,727 discloses a manufacturing method for forming metal articles. Disclosed therein is a reinforcement insert which is located in a mold into which molten metal is poured. The reinforcement insert is incorporated in the piston crown at the crown surface. UK Patent Specification 1 224 577 discloses a piston in which radial heat expansion of the piston skirt is regulated by inserts extending substantially parallel with the curvature of the skirt and made from a material with a lower heat expansion coefficient than the piston body, e.g. inserts of steel. The inserts extend axially from the piston up to the lowest piston ring groove situated closest to the piston skirt. The inserts extend in a peripheral direction from the gudgeon bosses in both directions. Thus, a significant portion of the inside of the piston body is unlined. Japanese patent document 59-39346 discloses a piston body which incorporates a stress control plate extending partially over an internal surface of the piston.
In light of such prior art approaches, there remains a need for a reinforcing liner which conforms to the entire inside surface of the piston. Such a liner would provide increased dimensional stability during casting, machining, engine assembly, and in service. Also, there lingers an unsatisfied requirement for still further reduction in piston weight without sacrificing strength.